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Lipase-catalyzed organic reactions have been widely practiced in the past three decades. Especially interesting are insoluble/immobilized forms due to providing a possibility of facile use and recyclability, thus reducing process costs, and making the procedure more environmentally friendly. Carbon-based supports have been extensively exploited for this purpose, because of neutral and biodegradable nature and thermal and chemical stability. Their high specific surface area, characteristic surface morphology and lower mass transfer resistances play a vital role in the performance of the attached enzyme. This review paper presents an overview of the main aspects of lipase immobilized on multi-walled carbon nanotubes (MWCNTs). Moreover, different immobilization strategies to achieve a biocatalyst with improved performances are discussed. Furthermore, as lipases are considered to have high commercial worth for synthesis of valuable organic molecules, the second part of the paper is dedicated to the overview of the most important industrial sectors in which these nanobiocatalysts have been used. In specific, applications in biodiesel production, flavour ester synthesis and racemization are summarize

Adsorption of anthraquinone dye Acid Blue 111 by alumina-iron oxide doped particles prepared by sol-gel method from aqueous solutions was studied. The adsorbent morphology was revealed by FESEM and the crystallographic phase is analyzed by the XRD technique. The effect of adsorbate and adsorbent concentrations, pH value, type of adsorbent and thermodynamic parameters on dye removal by adsorption was studied. The change of dye concentration during the adsorbtion was followed using the UV-Visible spectrophotometer. The change of the adsorbent surface before and after dye removal was observed using the Fourier Transformation-infrared spectroscopy (FT-IR). The adsorption kinetics is in accordance with the pseudo-second-order kinetics model. The Langmuir and Freundlich adsorption isotherm models were used to describe the adsorption process. The thermodynamic study of dye adsorption proves the process is spontaneous with exothermic nature.

In recent decades an increase usage of chemicals in many ways of modern life is evident. So, the possibility of its intake into organisms, human and animals poisoning and health damage, is nowadays on a high level, especially when it comes to disaster situations caused by using toxic chemicals in terrorist attacks or for military purposes. If we look ahead, the risk of pesticide contamination of the water and soil, as one of the most important resources for surviving, is always present. The wide spectra of pesticide negative effects on the environment initiate the increasing number of investigations of efficient pesticide removal methods, especially from water. The aim of this study was to investigate the efficiency of direct electrochemical oxidation as a method for in-situ degradation of pesticides in the aquatic environment, depending on the concentration of pesticides, present electrolytes, applied current and the pH value of the medium. As a model molecule, the neonicotinoid pesticide thiamethoxam was used. Kinetics of thiamethoxam degradation in aqueous solution was followed by UV/Vis spectrometry.

Nicosulfuron, a sulfonylurea herbicide, was subjected to different Fenton reactions at pH of a nicosulfuron aqueous solution (pH 5). Usually, the optimal pH for the Fenton reaction is between 3 and 4, but the addition of acids is not environmentally acceptable. This is the reason why the reactions were performed at a higher pH value than usual. So, classical Fenton and Fenton-like reactions were applied as well as photo-Fenton and photo-Fenton-like reactions. In addition, microwave Fenton and Fenton-like reactions were used in nicosulfuron degradation. Influences of Fe2+ and Fe3+ concentrations, as well as hydrogen peroxide concentrations, were studied. The Fenton reaction was much faster and more efficient than the Fenton-like reaction, while the photo- Fenton reaction proceeded much faster and more efficiently than the Fenton reaction. The microwave-Fenton and microwave-Fenton-like reactions proceeded with increased efficiency in comparison to the Fenton and Fenton-like reactions. The phytotoxicity and acute toxicity of the reaction products of nicosulfuron oxidation by the photo-Fenton reaction were analyzed. The toxicity testing of nicosulfuron treatment by photo-Fenton process showed a decrease in phytotoxicity, while the acute toxicity tests showed that the samples after treatment had lower toxicity. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 172013, Grant no. 172007 and Grant no. III 46008]

The problem of environmental pollution day by day becomes more worrisome, primarily due to the large amounts of wastewater contaminated with various harmful organic compounds, discharged into the environment untreated or partially clean. Feasibility of use of horseradish peroxidase (Amoracia rusticana) in the synthetic dyes decolorization was approved by many researchers. Among a number of supports used for the immobilization, it was found that natural clay, kaolin has excellent features which are a precondition for obtaining biocatalysts with the excellent performances. For this reason, a horseradish peroxidase was immobilized onto kaolin using glutaraldehyde as a cross-linking agent. Obtained biocatalyst was applied in the decolorization of anthraquinone dye C. I. Acid Violet 109. Under determined optimal conditions (pH 4.0, hydrogen peroxide concentration 0.6 mM, dye concentration 30 mg L-1, temperature 24ºC) around 76 % of dye decolorization was achieved. Reusability study showed that resulting biocatalyst was possible to apply four times in the desired reaction with relatively high decolorization percentage. [Projekat Ministarstva nauke Republike Srbije, br. III-46010 i br. 172013]

This study describes the investigation of degradation products of donepezil (DP) using stability indicating RP-HPLC method for determination of donepezil, which is a centrally acting reversible acetylcholinesterase inhibitor. In order to investigate the stability of drug and formed degradation products, a forced degradation study of drug sample and finished product under different forced degradation conditions has been conducted. Donepezil hydrochloride and donepezil tablets were subjected to stress degradation conditions recommended by International Conference on Harmonization (ICH). Donepezil hydrochloride solutions were subjected to acid and alkali hydrolysis, chemical oxidation and thermal degradation. Significant degradation was observed under alkali hydrolysis and oxidative degradation conditions. Additional degradation products were observed under the conditions of oxidative degradation. The degradation products observed during forced degradation studies were monitored using the high performance liquid chromatography (HPLC) method developed. The parent method was modified in order to obtain LC-MS compatible method which was used to identify the degradation products from forced degradation samples using high resolution mass spectrometry. The mass spectrum provided the precise mass from which derived molecular formula of drug substance and degradation products formed and proved the specificity of the method unambiguously. [Projekat Ministarstva nauke Republike Srbije, br. 172013]

Electrochemical decolorization of the Reactive Orange 16 was studied using dimensionally stable Ti/PtOx anode in the chloride containing solution. Different reaction parameters, agitation speed, applied current, sodium chloride concentration, and dye concentration was varied and optimum electrolysis conditions were suggested. The hypohlorous acid was suggested to be an active species in the electrochemical decolorization. Reaction was also studied using UV-Vis spectrophotometry, high-pressure liquid chromatography (HPLC), and total organic carbon (TOC) and total nitrogen (TN) analyses. [Projekat Ministarstva nauke Republike Srbije, br. ON172013 i br. ON172046]

2-Pyridones are important heterocyclic compounds that are widely used in medical chemistry, and their various derivatives have significant biological and medical applications. In this paper, the synthesis of 2-pyridones as well as 2-pyridone based compounds such as 2-quinolones using microwave assisted organic chemistry is reviewed. The review is divided in three parts. In the first part, microwave synthesis of 2-pyridones according to the type of condensation is discussed. In the second part, microwave assisted synthesis of 2-quionolones is listed. At the end of the review several examples of microwave synthesis of other 2-pyridone based compounds (ring fused N-substituted 2-pyridones) are given. [Projekat Ministarstva nauke Republike Srbije, br. 172013]

An isocratic, reversed-phase liquid chromatographic method was applied for the investigation of the degradation products of amlodipine besylate under the stressed conditions in solution. Amlodipine besylate stock solutions were subjected to acid and alkali hydrolysis, chemical oxidation and photodegradation as well as to the electrochemical degradation by cyclic voltammetry in 0.05 mol/L NaHCO3 on gold electrode. The total degradation of amlodipine besylate was achieved in 5 mol/L NaOH at 80°C for 6 h and the compound with molecular formula C15H16NOCl was identified as a main degradation product. Under acidic (5 mol/L HCl at 80°C for 6 h) stress conditions 75.2% of amlodipine besylate degradation was recorded. Oxidative degradation in the solution of 3% H2O2-methanol 80:20 at 80°C for 6 h showed that amlodipine besylate degraded to 80.1%. After 14 days of expose in photostability chamber amlodipine besylate solution showed degradation of 32.2%. In electrochemical degradation after 9 hours of cyclization the beginning of amlodipine oxidation was shifted for 200 mV to more negative potentials, with the degradation of 66.5%. Mass spectrometry analysis confirmed the presence of dehydro amlodipine derivate with molecular formula C20H23N2O5Cl in oxidative and acidic conditions while in electrochemical degradation was detected in traces. [Projekat Ministarsva nauke Republike Srbije, br. 172013]

Flotation reagents can be transformed to industrial waste if they are stored for a long period of time. Also, if synthesis or drying process is not performed under defined conditions in industrial plants, which produce flotation reagents, batch of waste may arise and be stored as a waste. The chemical composition of this waste depends on the phase in which it was created, but typically includes: unreacted alkali hydroxide, solvent - alcohol and trithiocarbonate and oxidation product - dixanthogenate. In this paper a new laboratory procedure for the treatment of such wastes is described. The identification and separation of industrial waste components is also included. From the separated dixantogenate and xanthate a laboratory synthesis of thioncarbamates is given. In addition, a semi-industrial treatment of waste xanthate is presented. Synthesis of N-alkyl and N,N-dialkyl-O-isobutylthioncarbamates were obtained from the filtrate obtained in the first step. As a by-product, sodium thioglycolate was produced. This by-product is transformed to a thioglycolic acid by the addition of an acid. Also, the synthesis of thioncarbamates from dixanthogenates, isolated from industrial waste as a cake, is desribed. Described waste treatment is additionally interesting due to the production of sulphur as another by-product. Laboratory synthesis gave thioncarbamates in yields from 69.7 to 87.7 %, while the semi-industrial process for the selected batches produced thioncarbamates in yields from 74.2 to 80.5 %. Taking into account the importance of the synthesized compounds as selective flotation reagents, a new procedure of their synthesis from industrial waste is characterized by good yields and purity of the obtained compounds, the simplicity of process, low environmental impact and short reaction times of synthesis. [Projekat Ministarstva nauke Republike Srbije, br. III 43007]

Electrocatalytic decolorization of the arylazo pyridone dyes has been investigated in the presence of sodium chloride using DSA Ti/PtOx electrode in the diluted sodium hydroxide. Decolorization can be attributed to the indirect oxidation of the investigated dyes by the electrogenerated hypochlorite formed from the chloride oxidation. Electrochemical decolorization has been investigated for the different sodium hydroxide concentration in the range from 40 mg dm-3 to 4 g dm-3, sodium chloride concentration in the range from 15 to 40 g dm-3, agitation speed in the range from 150 to 500 rpm, currents in the range of 100 to 250 mA, and dye concentration from 5 to 20 mg dm-3. The optimum electrolysis conditions have been suggested. Effect of substituents on the reaction rate has also been studied. [Projekat Ministarstva nauke Republike Srbije, br. OI172013, OI172046]

3-Cyano-4-ethoxymethyl-6-methyl-2-pyridone is an important precursor in the synthesis of vitamin B6, obtained in the addition reaction between 2-cyanoacetamide and 1-ethoxy-2,4-pentanedione catalyzed by lipase from Candida rugosa (triacylglycerol ester hydrolases, EC 3.1.1.3). This work shows new experimental data and mathematical modeling of lipase catalyzed synthesis of 3-cyano-4-ethoxymethyl-6-methyl-2-pyridone, starting from 1-ethoxy-2,4-pentanedione and 2-cyanoacetamide. Kinetic measurements were done at 50 oC with enzyme concentration of 1.2 % w/v. Experimental results were fitted with two kinetic models: the ordered bi-ter and ping-pong bi-ter model, and the initial rates of the reaction were found to correlate best with a ping-pong bi-ter mechanism with inhibition by 2-cyanoacetamide. Obtained specificity constants indicated that lipase from C. rugosa had higher affinity towards 1-ethoxy-2,4-pentanedione and less bulky substrates. [Projekat Ministarstva nauke Republike Srbije, br. 172013, br. III 46010 and br. 172049]

The determination of clopidogrel, an antiplatelet agent, was performed at a gold electrode in pH 3.7 acetate buffer using cyclic voltammetry (CV) and square wave voltammetry (SWV). Each voltammogram is characterized by the well defined peak at approximately 1.0 V. The current of anodic stripping peak exhibits linear dependence on the clopidogrel concentration in a range from 317.89 mg cm-3 to 935.16 mg cm-3. The obtained linearity was applied to determine clopidogrel amount in the tablet form of pharmaceutical preparation (Plavix®). The results were compared to the UV spectrophotometric and HPLC method. [Projekat Ministarstva nauke republike Srbije, br. ON172013]

Linear free energy relationships (LFER) were applied to the IR, 1H and 13C NMR spectral data of N-(substituted phenyl)-2-cyanoacetamides. A variety of substituents were employed for phenyl substitution and fairly good correlations were obtained using the simple Hammett and the Hammett-Taft dual substituent parameter equations. The correlation results of the substituent induced 13C NMR chemical shifts (SCS) of the C1, C=O and N-H atom indicated different sensitivity with respect to electronic substituent effects. A better correlation of the SCSC=O with a combination of electrophilic and nucleophilic substituent constants indicated a significant contribution of extended resonance interaction (π-delocalization) within the π1-unit. The conformations of the investigated compounds were studied using the DFT B3LYP/6-311G method and, together with the results of 13C NMR and IR spectroscopic studies, a better insight into the influence of such a structure on the transmission of electronic substituent effects was obtained.

Milrinone, 1,6-dihydro-2-methyl-6-oxo-[3,4’-bipyridine]-5-carbonitrile, is a positive inotropic cardiotonic agent with vasodilator properties that acts as selective phosphodiesterase 3 inhibitor in cardiac and vascular smooth muscle. Trade names of milrinone are Primacor, Corotrop, Corotrope, and Milrila. Milrinone, an amrinone derivative, is 20 to 50 times more active than amrinone and possesses reduced propensity to side effects. The use of milrinone has created controversy in the medical as the result of increased mortality rate among patients that received high amounts of milrinone in oral form. Reaserch show that it can be benifitial for patients with severe congestive heart failure when used as short-time intravenous therapy. Milrinone properties, stability, as well as mechanism of action and synthesis under laboratory and industry conditions have been described in this paper. For industrial purposes milrinone is synthesized by condensation of cyanoacetamide with 4-(dimethylamino)-3-(4-pyridinyl)-3-buten-2-one and 4-ethoxy-3-(4-pyridinyl)-3-buten-2-one in presence of a base, or by the reaction of 1-(4-pyridinyl)- 2-propanone with ethoxymethylenmalononitrile or 4-alkoxy-3-(4-pyridinyl)-3-buten-2-one with malononitrile without the use of external base. The starting compound for these syntheses is 4-picoline. Alternative synthesis of milrinone starts from 2-methyl-3-(4-pyridylidiene)-1,1,5-tricyano-1,4-pentadiene-5-carboxamide and 2-methyl-6-oxo-1,6-dihydro-3,4’-bipyridine-5-carboxamide. Lastly, methods for milrinone synthesis in laboratory, injection preparation and purification have been summarized.

The catalytic abilities of gold electrode were tested for the quantitative determination of amphetamine (A) and 3,4-methylenedioxy-N-methylamphetamine (MDMA) standards by their oxidation using cyclic voltammetry (CV). The value of the oxidative currents of A and MDMA standards at 0.80 V vs. SCE in 0.05 M NaHCO3 at the scan rate of 50 mV/s is linear function of concentration in range of 110.9-258.9 mM and 38.7-229.2 mM, respectively. Square wave voltammetry (SWV) revealed linear increase of current with concentration of MDMA (range 30.9-91.6 mM) and thus quantitative determination of amphetamine derivates. SWV analysis is successfully performed in spiked urine samples as well. A and MDMA in the presence of sucrose and as a content in illegally produced tablets were also analyzed. The voltammetric determination of A and MDMA derivatives using CV and SWV at gold electrode is a rapid, selective and simple procedure and its accuracy was confirmed with reference method, high performance liquid chromatography (HPLC). The spiked urine samples analysis offers additional possibility for the rapid detection of A and MDMA in human urine.

In the last three or four decades disperse dyes derived from pyridones (in particular azo pyridone dyes) have gained in importance, and are widely used in various fields. These compounds have excellent coloration properties, and are suitable for the dyeing of polyester fabrics. Basic features of these dyes are simplicity of their synthesis by diazotation and azo coupling. They generally have high molar extinction coefficient with medium to high light and wet fastness. The absorption maxima of these dyes show their visible absorption wavelength ranging from yellow to orange, which can be attributed to poorly delocalized electrons in the pyridone ring. However, there are several dyes with deep colors such as red or violet. Pyridone dyes with alkyl and aryl groups in ortho position to azo group show 2-pyridone/2-hydroxypyridine tautomerism, while those containing OH and NHR groups conjugated with the azo group show azo-hydrazone tautomerism. Determining azo-hydrazone tautomerism could be therefore interesting, since the tautomers have different physico-chemical properties and most importantly different coloration. The literature on azo-hydrazone tautomerism, determination of equilibrium position, and investigation of substituent and solvent influence on tautomerism has been summarized in the presented review. The general conclusion is that the equilibrium between two tautomers is influenced by the structure of the compounds and by the solvents used. The tautomeric behavior patterns of the arylazo pyridone dyes in the reviewed literature has been studied using various instrumental techniques, including FT-IR, UV-vis, and NMR spectroscopy. The quantum chemical calculations related to the azo-hydrazon tautomerism have also been included. A large number of pyridone dyes exist in hydrazone form in solid state, while in solvents there is a mixture of tautomers. In addition, the X-ray single-crystal diffraction data analysis of some commercial pyridone dyes has been discussed concluding that they all crystallize in the hydrazone form.

Lipases are very efficient biocatalysts with wide application in synthesis of important ingredients of food, cosmetics and pharmaceutical products, due to their capacity to catalyze both, ester synthesis and ester hydrolysis. The preparation of stable and active immobilized derivatives of lipases is necessity for their application in industrial enzymatic processes. In this work, the optimization of lipase from C. rugosa immobilization by microwave irradiation was performed, since it was previously reported that immobilization process can be drastically accelerated by means of microwave irradiation, even resulting with slight increase of lipase activity. Eupergit®, commercial support with active epoxy groups, was used as immobilization support. In first stage of our study, the immobilization time and ionic strength of immobilization buffer were optimized. It was found out that the highest immobilized activity can be achieved at high ionic strengths (1 M buffer) after 3 min, while further increase of immobilization time led to decrease of lipase activity. Then, the immobilized derivative obtained at optimum conditions was applied in synthesis of amyl isobutyrate in organic solvent. Key reaction factors (temperature, water concentration, immobilized lipase concentration, and substrate molar ratio) were optimized using response surface methodology. The substrate conversion higher above 85% was achieved in our study. The statistical analysis revealed that each of analyzed factors had significant effect on yield of ester, with initial enzyme concentration and substrate molar ratio being the most prominent factors. The second-order regression model that describes the effect of all four factors on substrate conversion was established. The optimum values of factors were: temperature 50ºC, initial immobilized enzyme concentration 220 mg ml-1, added water concentration 0.1% (v/v), and molar ratio acid/alcohol 2.5.

A gold electrode was applied in the voltammetric determination of oseltamivir phosphate standard in 0.05 M NaHCO3. Oseltamivir phosphate as a standard and as a component of Tamiflu® capsule exhibited the identical cyclic voltammogram. The peaks originated from excipients in capsule do not appear under the applied electrochemical conditions. The electrochemical method for the qualitative determination of oseltamivir phosphate in Tamiflu® capsule by cyclic voltammetry was developed. The presence of oseltamivir phosphate as standard and as a content of Tamiflu® capsule in electrolyte as well as their concentrations were simultaneously checked by HPLC. The lack of the current/concentration dependency was established. The not pretreated glassy carbon electrode cannot be used for the determination of oseltamivir phosphate under identical experimental conditions presented for gold electrode.

The discovery of carbon nanotubes (CNTs) has opened a new door in nanotechnology. With their high surface area, unique electronic, thermal and mechanical properties, CNTs have been widely used as carriers for protein immobilization. In fact, carbon nanotubes present ideal support system without diffusional limitations, and also have the possibility of surface covalent functionalization. It is usually the oxidation process that introduces carboxylic acid groups. Enzymes and other proteins could be adsorbed or covalently attached onto carbon nanotubes. Adsorption of enzyme is a very simple and inexpensive immobilization method and there are no chemical changes of the protein. It has also been found that this technique does not alter structure and unique properties of nanotubes. However, a major problem in process designing is relatively low stability of immobilized protein and desorption from the carrier. On the other hand, while covalent immobilization provides durable attachment the oxidation process can reduce mechanical and electronic properties of carbon nanotubes. It can also affect the active site of enzyme and cause the loss of enzyme activity. Bioimmobilization studies have showed that there are strong interactions between carbon nanotubes surface and protein. The retention of enzyme structure and activity is critical for their application and it is of fundamental interest to understand the nature of these interactions. Atomic force microscopy (AFM), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and circular dichroism (CD) spectroscopy provide an insight into the structural changes that occur during the immobilization. The aim of this paper is to summarize progress of protein immobilization onto carbon nanotubes.

Over 50% of all colorants which are used nowdays are azo dyes and pigments, and among them arylazo pyridone dyes (and pigments) have became of interest in last several decades due to the high molar extinction coefficient, and the medium to high light and wet fastness properties. They find application generally as disperse dyes. The importance of disperse dyes increased in the 1970s and 1980s due to the use of polyester and nylon as the main synthetic fibers. Also, disperse dyes were used rapidly since 1970 in inks for the heat-transfer printing of polyester. The main synthetic route for the preparation of azo dyes is coupling reaction between an aromatic diazo compound and a coupling component. Of all dyes manufactured, about 60% are produced by this reaction. Arylazo pyridone dyes can be prepared from pyridone moiety as a coupling component, where substituent can be on nitrogen, and diazonim salts which can be derived from different substituted anilines or other heterocyclic derivatives. In addition, arylazo dyes containing pyridone ring can be prepared from arylazo diketones or arylazo ketoesters (obtained by coupling β-diketones or β-ketoesters with diazonim salts) by condensation with cyanoacetamide. Disazo dyes can be prepared by tetrazotizing a dianiline and coupling it with a pyridone or by diazotizing aniline and coupling it with a dipyridone. Trisazo dyes can be also prepared by diazotizing of aniline and coupling it with a tripyridone or by hexazotizing a trianiline and coupling it with a pyridone. The main goal of this paper is to give a brief review on the synthesis of arylazo pyridone dyes due to the lack of such reviews. In addition, some properties of arylazo pyridone dyes as light fastness and azo-hydrazon tautomerism are disccused.

Monoacylglycerols are non-ionic surfactants widely used in the food industry. They are also important in cosmetic and pharmaceutical industries as drug carriers and for the consistency improvements in creams and lotions. Current process for their production is based on the glycerolysis of natural fats and oils in the presence of inorganic catalysts at temperatures higher than 220 oC. The major drawbacks of this process include high-energy consumption, low yield, and poor product quality. The use of lipases for the monoacylglycerols production offers environmental advantages and a reduction in energy consumption. Besides, the same surfactants prepared by the enzymatic synthesis may be labeled as “natural”. Recent progress in the application of highly-stable lipases in the organic solvents offers the possibility of employing various methods to the enzyme-catalyzed synthesis of monoacylglycerols, such as selective hydrolysis of fats and oils using 1,3-regiospecific lipases, the esterification of glycerol with fatty acids and the glycerolysis of fats or oils. In this review, different reaction systems such as aqueous-organic two-phase systems, microemulsions and reverse micelles systems, anhydrous organic solvents, solvent-free systems with free or immobilized lipases, as well as the use of two-phase membrane reactor systems are presented. We discuss some of the key factors, such as the control of water content, removing of the products from reaction system, and the effects of solvent on the lipase activity and selectivity, that must be addressed in order to obtain an efficient reaction system with high yields of monoacylglycerols. Engineering of the enzymatic monoacylglycerols synthesis processes requires also optimization of other factors as: molar ratio of substrates, temperature, type of lipase immobilization and supports (if any), reactor design and operating regime.

The importance of vitamin B6 has been known since its discovery in the 1940's. Chemical tests, elestrometric titration determinations, and absorption spectrum studies showed that this vitamin exists in three major chemical forms: pyridoxine (an alcohol), pyridoxal (an aldehyde), and pyridoxamine (a primary amine). Vitamin B6 is needed for more than 100 enzymes involved in protein metabolism, and it is assumed that this vitamin is cofactor of metabolic processes more important than any other substance. A deficiency of vitamin B6 in the human diet leads to severe disorders. Vitamin B6 is necessary for the proper function of the immune and nervous system, and helps the body convert protein to energy. This paper describes the history, properties and applications of vitamin B6, elucidation of chemical structure, and different procedures for synthesis of pyridoxine and pyridoxamine.

A gold electrode was used for the qualitative and quantitative electrochemical determination of analytical methomyl in a neutral electrolyte (0.050 M NaHCO3) using cyclic linear sweep voltammetry. In the potential range from -800 mV vs. SCE to 1000 mV vs. SCE the analytical methomyl was quantitatively determined in the concentration range 4.0-16 mg L-1. In the potential range from -1300 mV vs. SCE to 1300 mV vs. SCE, methomyl was qualitatively determined by two anodic and four cathodic reactions. Cycling the potential in this range for 150 min caused the degradation of the molecule, which was confirmed by HPLC analysis. On the other hand, technical methomyl exhibited an inhibition of the gold electrode surface due to the impurities.

N-Phenyl-2-phenylacetamide was alkylated with benzyl chloride in the presence of powdered potassium hydroxide under microwave irradiation in a solvent-free system. The reactions were also performed in the presence of phase-transfer catalysts. The formation of N-, O- and C-products of alkylation was followed by gas chromatography. The N-product was found to be the main product under microwave irradiation. The O-product was obtained in higher yields when an excess of base and benzyl chloride was used.

The 13C- and 1H-NMR chemical shifts of thirteen N(1)-(4-substituted phenyl)-3-cyano-4,6-dimethyl-2-pyridones were measured in deuterated dimethyl sulfoxide (DMSO-d6). The correlation analysis for the substituent-induced chemical shifts (SCS) with σp, inductive (σI) and different scale of resonance (σR) parameters were performed using the SSP (single substituent parameter), DSP (dual substituent parameter) and DSP-NLR (dual substituent parameter-non-linear resonance) methods. The results of the calculations concerning the polar and resonance effects satisfactorily describe the substituent effects at the carbon atoms of interest. The mode of transmission of the substituent effects, both inductive and resonance, in relation to the geometry of the investigated pyridones is discussed.

Lipase-catalyzed synthesis of esters has been widely investigated due to numerous advantages in comparison with the conventional chemical process catalyzed with concentrated acids since use of chemical catalysts leads to several problems. The most important disadvantages are corrosion of equipment, hazards of handling of the corrosive acids that are not reused, loss of conversion, yield and selectivity. The activity of water in reaction mixture seems to be one of the crucial factors affecting yield of enzymatic synthesis, since the excess of water promotes hydrolysis of the ester. Therefore, a significant part of related studies was focused on attempts to increase the yield of esters by efficient control of water activity. In our experimental work an attempt was made to regulate the activity of water by addition of water adsorbents in reaction mixture for synthesis of amyl isobutyrate. Two adsorbents were used: silica gel and molecular sieves (zeolites). The use of water adsorbents was optimized with respect to timing of adsorbent addition and pretreatment of adsorbent. The pretreatment of adsorbent with substrate did not increase the yield of ester. It was found that the timing of adsorbent addition is crucial factor. The addition in early phases of reaction leads to the decrease in ester yield compared to reaction without adsorbents. On the other hand, when the adsorbent was added in the late stage of reaction it exhibited beneficial influence on the yield of ester. The increase of yield was higher with silica gel (10%) than with molecular sieves (3.5%). These discrepancies can be ascribed to higher water adsorbing capacity of silica gel in systems with higher water content. Superior behavior of silica gel in ester synthesis in conjunction with simple process of regeneration recommends the use of this adsorbent for increasing the yield of lipase-catalyzed ester synthesis.

The object of the study was to investigate the process conditions relevant for the pentyl octanoate production with the lipase from Candida rugosa immobilized on Sepabeads EC-EP carrier. This is an epoxide-containing commercial polymethacrylic carrier with suitable characteristics for enzyme immobilization. The immobilized lipase suitable for pentyl octanoate synthesis has been prepared by a direct lipase binding to polymers via their epoxide groups. The enzymatic activity was determined by both hydrolysis of olive oil in an aqueous system and esterification of n-pentanol with octanoic acid in a low aqueous system. The influence of several important reaction parameters such as temperature, initial water content, initial substrate molar ratio, enzyme loading and time of adding of molecular sieves in the system is carefully analyzed by means of an experimental design. Production of the ester was optimized and an ester production response equation was obtained, making it possible to predict ester yields from known values of the five main factors. Almost complete conversion (>99%) of the substrate to ester could be realized, using lipase loading as low as 37 mg/g dry support and in a relatively short time (24 h) at 45ºC, when high initial substrate molar ratio of 2.2 is used.

Organic solvents may appear in wastewaters and other industrial waste streams containing dyes, therefore, their photodegradation catalyzed by TiO2 should be investigated. Solvent effect on photodegradation of CI Reactive Orange 16 has been studied using simulated solar light and P-25 TiO2. Methyl, ethyl and isopropyl alcohol as well as acetone were used as solvents. Photodegradation reaction was faster in methyl than in ethyl alcohol while in water was the slowest. RO16 photodegradation efficiency and reaction rate decreased in the presence of small concentration of ethanol. Higher photodegradation efficiency was observed for higher ethanol concentration. For acetone, photodegradation decreased as concentration of acetone increased. It seems that protic solvents at higher concentrations promote reaction, while at low concentrations slow down reaction. Aprotic solvents slow down reaction.

Environment friendly iron catalysts were applied in the decomposition reactions of some toxic compounds like phenol, methomyl and corbofuran pesticide. The applied catalytic processes belong to photo-Fenton reactions. Heterogeneous iron catalysts showed significant activity in phenol and methomyl conversion, however, these catalysts were completely inactive in destruction of carbofuran molecule, even in the catalytic reaction promoted with UV light at high temperature.

In this study, the feasibility of the synthesis of various flavor esters catalyzed by a commercial lipase from Candida rugosa was investigated and the process parameters were optimized. Lipase from C. rugosa successfully catalyzed the synthesis of 19 esters. The highest yields, of more than 90 % after 20 h, were observed in the synthesis of short-chain esters, pentyl propanoate, isopentyl butanoate, and butyl butanoate. Increasing the number of carbon atoms of both substrates above 8 caused a significant decrease of the initial reaction rates and the final yields. The enzyme showed surprisingly low affinity towards pentanoic acid and hexanoic acid, compared with the higher homologues, octanoic acid and decanoic acid. In addition to the number of carbon atoms, the structure of the substrates had a significant influence on the enzyme activity. Namely, the activity of the enzyme towards isopropanol was significantly lower compared with n-propanol. Additionally, cis-9-octadecenoic acid was a better substrate than octadecanoic acid, its saturated analogue.

The temperature dependence of the retention index was studied for n-alkyl esters of acetic, propionic, cyclohexanecarboxylic, benzoic and phenylacetic acid on DB-1 and DB-5 capillary columns. The study was performed over various temperature ranges depending on the volatility of the ester. Two linear equations of the temperature dependence of the retention data on the column temperature and its reciprocal as variables were studied. Agood linearity of the retention index versus column temperature was found.

A series of 1,3,5-trisubstituted isocyanurates (substituents: CH2CH2OH CH2CH=CH2 and CH2CH2COOH) was synthesized according to a modified literature procedure. Experimental investigations included modification of the synthetic procedure in terms of the starting materials, solvents, temperature isolation techniques, as well as purification and identification of the products. All the synthesized isocyanurates were identified by their melting point and FTIR, 1H NMR and UV spectroscopic data. Fourier transform infrared spectrophotometry was also used to study the interaction between ammonium perchlorate, hydroxyl terminated poly(butadiene), carboxyl terminated poly(butadiene), poly(butadiene-co-acrylonitrile), poly(propylene ether) cyclotrimethylenetrinitramine and the compounds synthesized in this work which can serve as bonding agents. The results show that tris(2-hydroxyethyl)isocyanurate is a universal bonding agent for the ammonium perchlorate/carboxyl terminated poly(butadiene)/cyclotrimethylenetrinitramine composite propellant system.

The photo degradation of synthetic dyes under visible and solar light as a method for the removal of synthetic dyes from water and wastewater was reviewed. The mechanisms of photo degradation are presented. The influence of catalysts, inorganic ions and other substances on photo degradation was discussed.

The usual way of applying heat to a chemical reaction is the use of a Bunsen burner, an oil or some other type of bath, or an electric heater. In inorganic chemistry, microwave technology has been used since the late 1970s while it has been implemented in organic chemistry since the mid-1980s. Microwave heating has been used in the food industry for almost fifty years. The shorter reaction times and expanded reaction range that is offered by microwave technology are suited to the increased demands in industry. For example, there is a requirement in the pharmaceutical industry for a higher number of a novel chemical entities to be produced, which requires chemists to employ a number of resources to reduce time for the production of compounds. Also, microwaves are used in the food industry, as well as in the pyrolysis of waste materials, sample preparation, the solvent extraction of natural products and the hydrolysis of proteins and peptides.

Benzylation of N-(4-chlorophenyl)-2-phenylacetamidewith benzyl chloride in the presence of powdered potassium hydroxide under various reaction conditions was performed in order to establish the possible reaction products. Different temperatures and ratios of reactants and solvents were used. The reactions were also carried out in the presence of different phase-transfer catalysts in toluene as a solvent. The formation of the reaction products was followed using gas chromatography. On the basis of the obtained results, the reactivity and the orientation in the alkylation reaction of the investigated amide is discussed.

Enalapril was originally synthesized by Merck Sharp and Dohme and is an angiotensin converting enzyme inhibitor. Thus, enalapril is used in the treatment of mild to severe hypertension. Enalapril is chemically (S)-1-[N-[1-(et-hoxycarbonyl)-3-phenylpropyl]-L-alanyl]-L-prolin and although the first synthesis was published in 1980, it can be obtained using different synthetic pathways. This paper describes the synthesis as well as the properties and stability of enalapril.

A series of alkyl 1,3-diketones were used to study the temperature dependence of the Kovats retention indices in the temperature range 130–190 ºC (403–463 K). The temperature dependence is described by the empirical equation I = B B/T + ClnT. On the basis of this equation, the activation enthalpy, ΔH≠, and the chemical potential of the partitioning of one methylene group between the two phases of the chromatographic system, Δμp(CH2), were calculated. Also the Kovats retention indices – boiling point correlations (linear and reciprocal) for alkyl 1,3-diketones were studied and Δμp(CH2) was calculated.

Various N-substituted phenylacetamides were alkylated using different alkylating agents under neutral and basic conditions. Reactions were performed at different reaction temperatures and in various solvents. Also, a number of various catalysts were used including phase-transfer catalysts. Reactions were followed using GC or GC-MS technique and the presence as well as the yields of the alkylation products were established. Generally, the best yield and high selectivity in the studied reactions were achieved under basic conditions where in the certain cases some products, mostly N-product were obtained solely in quantitative yields.

The temperature dependence of the retention index was studied for N-substituted amino s-triazines on DB-1, DB-5 and DB-WAX capillary columns within the temperature range 190–230 ºC. Two linear equations with the column temperature and its reciprocal as variables were studied. The first one shows a slightly better precision for 2,4-bis(alky lamino)-6-chloro-s-triazines and 2-alkylamino-4,6-dichloro-s-triazines while the second one shows a better precision for 2,4-bis(cycloalkylamino)-6-chloro-s-triazines.

The retention index increment for the addition of a methylene group to the alkyl group of an analyte molecule is shown to be lower than 100 i.u. for N-substituted amino s-triazines. In temperature programmed gas chromatography, a linearly interpolated retention index I, determined from the linear regression equation, I = AZ + (GRF)z, with the number of atoms (Z) in the molecule as variable, was used to describe the retention of 25 N-substituted amino s-triazines, on DB-1, DB-5 and DB-WAX capillary columns divided into five series according to the similarity of the alkyl groups in the particular series. In the above equation, A is the linear regression coefficient or the retention index increment per atom addition, Z the number of C,N and Cl atoms in the molecule, and (GRF)z the group retention factor or functionality constant for functional groups in the molecule, based on the number Z. It is possible to estimate the retention indices of an unknown member of the series from the Z, A and (GRF) values.

A series of 1,3-bis-substituted-5,5-dimethylhydantoins was synthesized using the reaction of 5,5-dimethylhydantoin with the corresponding alkyl halide in the presence of trimethylamine as catalyst and sodium hydroxide, according to a modified literature procedure. The experimental investigation included modification of the synthetic procedure in terms of starting materials solvent, temperature, isolation techniques, as well as purification and identification of the products. The absorption spectra of the 1,3-bis-substituted-5,5-dimethylhydantoins were recorded in twelve solvents in the range 200–400 nm. The effects of the solvent polarity and hydrogen bonding on the absorption spectra were interpreted by means of linear solvation energy relationships using a general equation of the form ν = ν0 s¶* + aα + bβ and by two-parameter models presented by the equation ν = ν0 s¶* + aα, where ¶* is a measure of the solvent polarity/polarisability, α is the scale of the solvent hydrogen bond donor acidities and β is the scale of the solvent hydrogen bond acceptor basicities. The solvent and substituent effects on the electronic absorption spectra of the investigated hydantoins is discussed.

Since its introduction in 1969, ibuprofen has become one of the most common painkillers in the world. Ibuprofen in an NSAID (non-steroidal anti-inflammatory drug) and like other drugs of its class it possesses analgetic, antipyretic and anti-inflammatory properties. While ibuprofen is a relatively simple molecule, there is still sufficient structural complexity to ensure that a large number of different synthetic approaches are possible. Since the introduction of pharmaceutical products containing ibuprofen, industrial and academic scientists have developed many potential production processes. This paper describes the history, synthesis and production, as well as the properties and stability of ibuprofen.

Acetylsalicylic acid is one of the most fascinating and versatile drugs known to medicine, as well as one of the oldest. Acetylsalicylic acid is a drug which is safe, with analgetic, antirheumatic, anti-inflammatory antiplatelet and antithrombotic action. It may be applied not only in clinical practice, but also as prevention. The first known use of an acetylsalicylic acid-like preparation can be traced to ancient Greece. In 1853 Charles Gerhardt published the first synthesis of acetylsalicylic acid. Felix Hoffmann, a chemist for Friedrich Bayer, a German dye company obtained a patent on acetylsalicylic acid some 40 years later. Bayer coined the name Aspirin for the new product. The 20 in century was the century in which many researchers in many companies tried to improve the synthesis of acetylsalicylic acid not only in terms of yield but also purity. This paper describes the history, use, mechanism of action, synthesis and production as well as the purification and stability of acetylsalicylic acid.

N-(4-Nitrophenyl)-2-phenylacetamide was alkylated with benzyl chloride in the presence of powdered potassium hydroxide at different temperatures and in various solvents in order to establish the reactivity and orientation in the reaction. The reactions were also carried out in the presence of different phase-transfer catalysts in toluene. Product formation was followed by GC. The obtained results were compared to the results of the benzylation of other N-substituted 2-phenylacetamides, especially of N-phenyl-2-phenylacetamide.

Catalysis in the synthesis of Pharmaceuticals and line chemicals nowadays becomes more and more important. Synthesis that minimizes wastes is important from the economical aspect, as well as from the environmental aspect. "Green chemistry" or "green technology" is an effort to protect the environment by increasing the efficiency of the overall synthetic processes in the chemical industry by minimizing or eliminating wasteful by-products. Modern catalytic methods in the synthesis of some Pharmaceuticals and fine chemicals are discussed such as phase-transfer catalysis, biocatalysis asymmetric catalysis and, generally, solid-phase chemistry.

A number of 5-substituted-4-methyl-3-cyano-6-hydroxy-2-pyridones from cyanoacetamide and the corresponding alkyl ethyl acetoacetates were synthesized according to modified literature procedures. The alkyl ethyl acetoacetates were obtained by the reaction of C-alkylation of ethyl acetoacetate. An investigation of the reaction conditions for the synthesis of 4-methyl-3-cyano-6-hydroxy-2-pyridone from cyanoacetamide and ethyl acetoacetate in eight different solvents was also performed. The ultraviolet absorption spectra of synthesized pyridones were measured in nine different solvents in the range 200-400 nm. The effects of solvent polarity and hydrogen bonding on the absorption spectra are interpreted by means of linear solvation energy relationships using a general equation of the form v = vo + sπ*+aα+bβ, where π* is a measure of the solvent polarity, α is the scale of the solvent hydrogen bond donor acidities and β is the scale of the solvent hydrogen bond acceptor basicities.